Feedworks and improvements therein



Feb. 9, 1965 J. c. NEILSON FEEDWORKS AND IMPROVEMENTS THEREIN 2 Sheets-Sheer. 1

Filed May 22, 1963 INVENTOR.

JAY c. NEILSON BY 4% HIS ATTORNEY Feb 9, 1965 J. c. NEILSON 3 9 FEEDWORKS AND IMPROVEMENTS THEREIN Filed May 22, 1963 2 Sheets-Sheet 2 LO Q INVENTOR.

JAY C. NEILSON HIS ATTORNEY United States Patent 3,168,854 FEEDWORKS AND HWPROVEMENTS THEREHN Jay C. Neilson, Arvada, C0lo., assignor to Gardner Machines, lnc., Salt Lake City, Utah, a corporation of Utah Filed ,May 22, 1963, Ser. No. 282,274 2 Claims. ((31. 91-437) The present invention relates to improvements in feed Works for reciprocating a selected mass by a fluid-motor ram drive incorporating suitable valving means and, more particularly, to a new and improved feedworks wherein valve-control determining presence and direction of motor drive is effected by means superior to that heretofore used and, further, wherein cushioning means is provided the feedworks to meliorate the effects of momentum which occur when large masses are subjected to rapid deceleration when the supply of pressure fluid to the fluid motor is suddenly cut off, and fluid return suddenly cut off, after a period of actuation.

Accordingly, an object of the present invention is to provide an improved feedworks for moving large masses, such as logs at a saw mill, wherein braking of the mass accommodated may be easily and smoothly performed.

A further object of the present invention is to provide, in general, an improved feedworks for saw mills and for other uses wherein large masses are translated back and forth.

A further object of the invention is to provide pneumatic cushioning means for feedworks in the hydraulic circuits thereof, wherein braking characteristics are optimised.

A further object of the invention is to provide a cushioning means for a hydraulic feedworks of the reciprocating type wherein, by suitable by-pass metering means and pneumatic means, the rapid decelerations of the mass accommodated may be compensated for by a unique cushioning action, and this for both directions of travel by the mass.

A further object of the invention is to provide a new and improved feedworks of, the hydraulic ram type for saw mills which will permit logs or other lumber, for example, to be translated selectively back and forth at any desired speed, in any time cycle, and for any given duration of stroke, and this in a manner such that smooth and accurate braking is possible for all speeds of translation and reciprocation desired.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings in which:

FIGURE 1 is a fragmentary plan view, partially cut away and sectioned for convenience of illustration of a feedworks incorporating the principles of the present invention.

FIGURE 2 is an enlarged section of the actuator employed in the structure of FIGURE 1 to reciprocate the control valve spool.

FIGURE 3 is an enlarged section, taken along the line 33 in FIGURE 1, of the cushioning mechanism of the invention.

In FIGURE 1 is shown a feedworks it) which may incorporate the present invention as indicated. Motor 11 drives a centrifugal pump 12the output flange 13 of which is bolted by bolts 14 to attachment flange 15 of reservoir 16. Reservior 16 may include any fluid but preferably is designed for use in a water system, for purposes of economy of operation. Member 17 is inteerr:

riorly hollow at 18 and forms an integral part of reservoir 16 to conduct liquid from pump 12 into chamber 19 of valve 29. A separate chamber 18, shown merely in dotted line, conducts liquid from reservoir in into the input of pump 12 so that the same may pump the liquid under pressure into valve chamber i Valve 20 and valve spool 21 thereof. are preferably identical to the composite valve 28 in the inventors issued patent, United States No. 3,049,147, issued Aug. 14, 1962.

Mounting flange 22 is bolted or otherwise secured to reservoir 16 as by bolt means 23 and securely mounts gun line 24 and return line 25, to which it is welded, to the reservoir such that these lines are disposed in communication with channels 25 and 26, respectively, of valve 20. Goose-necit 27 of return line 25 is afiixed to, abuts, or otherwise cooperatively engages gun line 24, and the line structure is secured in place by bolts 28 cooperating with packing gland flange 29 and flange .30. Reciprocating rod 31 is fixed by any conventional means to carriage 32 the latter of which is provided with conventional wheels 33 and axles 34 (one being shown) which accommodate the travel of carriage 32 upon tracks 35. As is well known in the art, the carriage 32 when in operation receives a log or other member to be cut and the frame is transported back and forth rapidly so that desired cuts therefrom may be formed.

Rod 31 includes a piston as which is interposed between end plates 36' respectively seated against shoulder 35 and secured in place by nut 36 threaded upon threads 37 of rod 31. In practice the piston 3 6 may be conveniently made of wood, preferably a hard wood, since the same will appropriately expand in the presence of water and hold a tight seal and, thereby, no extraneous seals need be used to seal the hydraulically operated, reciprocating structure.

Thus far there has been described presently-used feedworks in sawmill operations. The present invention contemplates the incorporation of desired improvements in such an advantageous feedworks. These improvements take the form of the incorporation of a novel actuator 39 and certain cushioning structure 4t), both about to be described.

Actuator 39 will be discussed first. The actuator together with its air system is indicated in FIGURE 2. In FIGURE 2 the actuator 39 includes a cylindrical body 40 and an actuator housing 41 threaded therein at threaded aperture 42 and sealed in place by O-ring 43. Disposed within cylindrical body at is a piston 44 having conventional piston rings 45. The piston 44 is secured upon actuator rod 46 by abutting the shoulder 47 thereof and by being secured in place by the incorporation of a ne ative (female) star-type lock washer 49 and by the threaded end 50 of rod 46 being threaded into centering rod 51. Centering rod 51 includes the hollow, threaded, receptacle portion 52 and also an elongate shaft portion 53 of reduced diameter with respect to the former and adjoining the same at shoulder 54. Shaft portion 53 receives washers 55 and 56 which serve as backing means for double-acting compression spring 57. Securement of the compression spring is made by retainer nut 58. A spacer 59 is disposed within the bore 6th of actuator housing 41 and abuts washer 55, serving as a limit stop for the spring mechanism. A tapered bushing retainer 61 is threaded into the end of actuator housing ll and itself receives a plug 62.

The cylindrical body 4%) is shown to be provided with pressed head H, sealingly journaling actuator rod 46, and with ports 63 and 64 which receive threaded fittings 65 and 66 of a control system 57' which preferably includes air conduit 58 and 59 jointly controlled by a three-position valve the valve receiving fluid pres sure and supply from source 61', such as a compressed air source, via conduit 62. Control handle 63 controls the action of valve 60' so that passageway 64 of the valve gate 65 Will either be closed, on neutral position, or connect source 61 either to conduit 58 or to conduit 59, this depending upon the position of handle 63, that is, whether it is turned counter-clockwise or clockwise from neutral position so that conduction to the respective conduit 58 and 59 is achieved.

As is heretofore explained in the inventors previous patent, United States Patent No. 3,049,147, there must be supplied a reciprocating means to reciprocate the valve spool 21 to accomplish the control necessary to reciprocatingly move, as desired, the carriage 32 by the extension and/ or withdrawal of reciprocating rod 31. The action of the valve has been heretofore explained in the above patent which is now fully incorporated herein by way of reference. The valve 20, when the valve spool 21 is displaced upwardly from its position in FIGURE 1, functions to introduce liquid under pressure through passageway 25 to gun line 24, thereby thrusting piston 36 and rod 31 outwardly and thereby causing the exhaust of liquid in front of, that is, to the left of piston 36 out of the return-line 25 back into the reservoir via valve 20 through passageway 26. This action occurs, again, when the valve spool 21 in FIGURE 1 is translated upwardly so as to admit the passing of fiuid from the pump 12 through chamber 18 and chamber 19 past the valve gate G involved and into chamber 25. This is fully explained in my patent above mentioned.

Now in order for this action to be terminated it is necessary that the valve 60 be returned to neutral position, which operates to close the fluid path, at both extremities, from and to the valve 20. Such closure produces a transient effect which, with the compensation therefor the present invention supplies, will be later described.

Subsequently, when it is desired to retrieve the carriage 32 so that piston 36 is to be driven to the right, toward the reservoir, then the valve spool 20 is translated downwardly from its central position shown in FIGURE 1 so as to permit return-line 25, passageway 26, chamber '70 and aperture 13 to coperate together to conduct liquid against the left side of piston 36 and force the liquid on the other side of piston 36 through valve 20 and into the reservoir.

Hence, there must be supplied a suitable actuator to accomplish the above described functions which will be very reliable, of low cost to manufacture, and operate in the precise manner intended.

The actuator 39 operates as follows. When valve 60' is in neutral position such that the valve spool 21 in FIGURE 1 is also in its neutral position as shown, no external pressure will be exerted on either side of piston 44, so that the pressure of spring 57 against washer 55 and spacer 59, and this same pressure exerted by the spring against washer 56 and shoulder 54, will position the actuator rod 46 as shown in FIGURE 2 so that the piston 44 will be in a central position as indicated. In order to thrust the piston 36 outwardly, that is to the left in FIGURE 1, so as to extend rod 31, the actuator rod 46 must be drawn inwardly with respect to cylinder body 40. This is accomplished by the operator rotationally displacing, at a speed and in a degree commensurate with the degree of acceleration and speed of gun line piston travel desired, the handle 63' in a clockwise direction so as to effect the communication of fluid source 61, such as a compressed air source, and the conduit 62' with conduit 59' (through the valve 60) and with orifice 64 communicating with Chamber G. This imposes a pressure on the right-hand side of piston 44 so as to draw the actuator rod 46 inwardly with respect to cylindrical body 40, thereby causing the compression of spring 57 against washer 55, since the latter abuts spacer 59. Hence, washer 56 and the entire actuator rod 46 will be translated to the left under the spring pressure of compression spring 57.

Upon the release of pressure, that is when the valve 60 is returned to neutral condition as shown in FIGURE 2, then there will be a release of air pressure against the right side of piston 44 so that the actuator rod 46 will be translated to its medial position as indicated in FIGURE 2, this under the action of spring 57, which action stops upon the abutment of washer 56 against shoulder 54. At this position the carriage 32 has been stopped in its travel and the rod 31 is extended outwardly. To retrieve rod 31 so that the carriage 32 is withdrawn, one need only rotationally displace valve control 63 in a counter-clockwise direction so as to apply air pressure through valve 60 and conduit 58' to the left hand side of piston 44 at chamber R. Such action translates piston 44 to the right in FIG- URE 2 so as to compress spring 57 under the action of the translation to the right of nut 58 and washer 55. However, once the lever 63 of valve 60' is again returned to neutral position, the actuator will return to the neutral state as shown in FIGURE 2, this under the compression of spring 57. Air escape from chambers R and G in valve neutral position is provided by valve bypass passageways 77' and 78'.

To complete the coupling of the actuator to the valve spool 21, a simple clevis coupler 78 and pins 74 and 75 need only be used to couple the actuator rod 46 at aperture 46' to the fixed stem extension 76 of valve spool 21. Groove 79 is provided for machining purposes and is not functionally related to the invention.

There will now be considered the cushioning structure for 40' in FIGURE 1 of the drawings. Reference is now made to FIGURE 3. In FIGURE 3 return line 25 and gun line 24 each include respective elongate cylinders 75 and 76 which are provided with stub risers 77 and 78 having attachment flanges 79 and 80, respectively; bolt attachments 81 and gaskets 82 accommodate the fixed, sealed securernent of the latter to flanges 83 and 84 which are welded to stub conduit 85 and 86, respectively. The stub conduit 85 and 86 are in turn welded to a cylindrical body 87 such that apertures 88 and 89 thereof communicate with the respective lines 25 and 24. Cylindrical body 87 includes flanges 90 and 91 welded thereto, the latter having bores 93 and 94 for centering the metering tube 95. Metering tube 95 includes a pluralities of apertures 96 and 97 at the respective ends thereof and additionally includes aperture pluralities 98 and 99 centrally thereof as indicated. More specifically, the aperture pluralities 98 and 99 are mutually spaced with respect to each other and are disposed a predetermined distance from the dimensional center (from line Z of the metering tube 95) that is on either side of closure head 100 of cushioning valve spool 101. Stern 102, in addition to including closure head 100, also includes piston-like lobes 103 and 104. It should be mentioned at this point that the spacing between the center line Z and at least some but preferably all portions of apertures 98, and this will apply to 99 also, will be at least equal to the degree of anticipated piston travel of the cushioning pistons 106 and 107.

Pistons 106 and 107 are preferably fabricated from wood and include O-ring seals 108 and 109, respectively, in the piston grooves 110 and 111 provided therefor. Each of the piston shafts 112 and 113 has annular grooves 114 and 115 which accommodate O-ring seal 116 and 117 disposed therewithin. The respective shafts 112 and 113 are supplied with shoulders 118 and 119 respectively which seat washers 120 and 121. Washers 122 and 123 back their respective pistons, and lock washers 124 and 125 and nuts 126 and 127 threaded onto the piston shafts 112 and 113 complete the piston and shaft structure. Air cylinders 128 and 129 are each provided with mounting flanges 130 and 131 which are respectively connected by through bolt attachments 132 and 133 to flanges 90 and 91 of cylindrical body 87 and also to disc-configured journal baflles 134 and 135 each of which serves as a cylinder cap for its respective air cylinder. Suitable O-ring seals as at -144'in the respective grooves shown provide #3 sealing means serving to seal the chambers between the journal baflles 134 and 135 from their respective air cylinders.

If desired there may be included upstanding bosses 146 and 147 which receive plugs 148 and 149, respectively. These plugs may be removed and test gages inserted for experimental purposes, if desired by the user: the plugs simply serve to cap desired, preliminary, air bleed-out through the respective bosses 146 and 147.

If desired, cylindrical spacers 150 and 151 may be used and be disposed in the ends of the respective air cylinders 128 and 125* to provide respective limit stop abutments for the two pistons 196 and 1117. The spacers 150 and 151 may, indeed, be smaller than the pistons, so long as the inside diameter of the latter clears the respective washers 122 and 123.

The operation of the structure FIGURE 3 is as follows. During the outward thrusting of piston 36 in FIGURE 1 to accomplish the extension of reciprocating rod 31 and carriage 32, pressured fluid will be passed by valve into the gun line 24 to accomplish such extension and, correspondingly, fluid will be returned through the return line 25 through the valve and into the reservoir. Now let us assume that the carriage is suddenly stopped by the operator adjusting air valve 60 appropriately in its neutral position so as to bring the lands of the valve gates of valve 20 into an alignment as shown in FIGURE 1. This produces an abrupt stopping of fluid supply to gun line 24 and a fluid return via return line 25. Absent suitable cushion means, considerable shock will at this point be experienced by the feedworks. However, and as will be noted in FIGURE 3, fluid will continue to flow through return line 25, by reason of its inertia and, since the valve 20 at this time will be closed, will flow upwardly through riser 77 and stub 85 to enter into chamber X and there proceed through apertures 96 and 98 to enter chamber X" and X, respectively. While there is a balancing of fluid pressure fiuid between lobe 103 and gate 100, there will be an exertion of pressure of the fluid in chamber X" against lobe 103, in a direction to the right of the viewer, so as to translate the valve spool 101 in the direction to the right. It is noted that there is a partition 160 separating chambers X and Y. The valve head 100 now commences to cross apertures 99, and fluid flowing up through apertures 98 into chamber X will proceed downwardly through apertures 99 into chamber Y and down into stub extension and riser 78 into the gun cylinder 76. This descent of fluid into the gun cylinder 76 will serve to accommodate continuous fluid flow and volume in the system and hence preclude the occurrence of a vacuum or reduced pressure condition as might exist between the valve and the outwardly traveling fluid because of the inertia of the carriage 32 and that which it is carrying, plus the equipment, when the same is decelerated suddenly. It will be observed that a slight vacuum area will almost always occur behind piston 36 in the gun line because of the advantageous relief for fluid returning to the now closed valve 20 provided by the cushioning mechanism, since there will now be some predisposition of the carriage 32, because of its inertia, to travel very slightly beyond that point which would otherwise be predetermined by the closing of valve 20. Hence, continuous fluid flow and fluid volume are assured in the present feedworks with its incorporation of the cushioning mech anism.

Correspondingly, when the rod 31 is withdrawn so as to pull carriage 32 to the right of the viewer in FIG- URE 1, then the fluid to the rear of piston 36 will be pushed thereby upwardly through riser 7S and stub conduit 86, since the valve 20 is again closed as shown in FIGURE 1, and will flow through chamber Y and into chambers Y and Y" via apertures @9 and 97, respectively, so as to urge, by virtue of the fluid pressure within chamber Y", the valve spool 101 in a direction to the left in FIGURE 3, thereby causing the valve head 1% to proceed over and past apertures 98 so as to permit fluid in chamber Y passing through apertures $9 into metering tube to proceed through apertures 98, once the valve head is passing thereover, down to chamber X and from thence through stub conduit 85 and riser 77 to the return cylinder 75 to fill such vacuum or reduced pressure area as may be caused by the continued, incremental rearward movement of piston 36 and the forward movement of fluid in return line 25 as caused by the inertia of the latter. It will be noted, therefore, that the operation accommodates not only the filling of a void, as it were, but, and more importantly, also supplies relief for the fluid approaching valve 20 when valve 20 is shut ofl.

It will be noted with reference to FIGURE 1 that the diameter of rod 31 is very small in comparison with the opening cross-section of the gun or piston line 24; hence, but little fluid is displaced by rod 31 as carriage 32 is withdrawn to the left and fluid is forced from the right end of piston 36 to the left end thereof (via 86Y-99 98-X-85). Such amount as is displaced, however, may be accommodated for by being received and stored in chamber Y and therein utilized for movement in a leftward direction (see FIGURE 3) of lobe 104 and hence piston 100 well past apertures 98. Slight fluid volume differences on alternate piston rod strokes (i.e. in an outward direction) may be accommodated for by the suitable dimensioning of chamber X" and positioning of lobe 163.

Alternatively, the inside diameter of line 25 (see FIG- URE 1) may be chosen to compensate for piston rod (31) fluid displacement.

Now it will be noted that the cushioning system may be a low-pressure, compressed air system so far as airbacking of the two cushion pistons 106 and 167 are concerned. It will be noted that as the valve spool 101 reciprocates back and forth in accordance with direction of fluid flow in the gun line and return line 25 and 24, there will be a corresponding outward urging of pistons 106 and 105 in accordance with the direction of movement of the valves spool. Each of these pistons is backed by air pressure which is multiplied at the inner end of shafts 112 and 113 by the ratio of the piston area to the shaft end area so that a large reaction pressure will be available at the areas of contact of the two shafts 112 and 113 with the respective ends of the valve spool 101. It is noted, further, that since the pistons 106 and 107 are independent, that independent pressures may be maintained in the respective air cylinders the magnitude of which will depend upon the degree of cushioning desired by the user for both extension and return of rod 31 in FIGURE 1. Nonetheless, the pressures within the respective air cylinders, though different, will maintain the valve spool 101 in central location when valve 20 is turned off after the initial transient interval has passed. Suitable fittings 175 and 176 are supplied the two air cylinders 128 and 129, and conduits 176 and 177, which can be equal pressure or different pressure lines, will lead to the air pressure supply 180. Suitable check valve means will be supplied at 181 and 182, as described.

Spacers and 151, again, merely limit the travel of the pistons 106 and 107, as desired.

For purposes of duration of long life and low friction characteristics it is preferable that the valve spool 101 be machined from brass and a steel cylindrical body 87 supplied. The piston shafts 112 and 113 are advantageously fabricated from mild steel and suitably chrome plated to prevent corrosion and otherwise contribute to long life. While the piston shafts and the valve spool 101 are physically separate, it is contemplated that they abut in central position after the transient period involved has elapsed as shown in FIGURE 3.

It is contemplated that compressed air or other compressed gaseous media be provided the cylinders 128 and 129 in the cushioning system of FIGURE 3. Fluids to be used in the gun and return line system will be liquids,

preferably water for purposes of economy of operation, but conceivably oil, hydraulic fluid, or suitable liquid substances. Preliminary to initial operation it is conceived that the reservoir in FIGURE 1 should be completely filled and the lines 25 and 24 filled also. Also to be pre-filled with liquid will be the fluid structure shown in FIGURE 3, this with the plugs 148 and 149 removed to accomplish air bleed-out. Once the system is free from air so far as the liquid chambers are concerned, then plugs 148 and 149 will be replaced.

The term feedworks used herein will be understood to refer not only to sawmill feedworks for reciprocating lumber to be cut, but, in the larger sense, to all fluid motor drives wherein a mass is to be selectively reciprocated.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. In a feedworks having a gun line, a return line disposed in communication with said gun line at a juncture therewith, a piston translationally disposed in said gun line, a reciprocable piston rod afiixed to said piston and disposed within, journaled by, and extending beyond said gun line and adapted to reciprocate an external given mass, and means afiixed to and disposed in communication with corresponding line portions of said gun cylinder and said return cylinder remote from said juncture for forcing liquid in said lines against said piston in opposite directions, alternately, for translating said piston; an improvement comprising a source of compressed gaseous media, and pneumatically controlled cushioning means coupled to said source and connected in automaticallyshunting circuit relationship with said gun cylinder and said return cylinder at said line portions for automatically shunting in a metered manner fluid approaching one of said line portions of said gun and return lines into the extremity of the remaining line, to thereby cushion transient fluid response, and wherein said pneumatically controlled cushioning means includes a cylindrical body, a pair of pneumatic cylinders fixedly disposed on opposite sides of said body, a pair of pneumatic pistons operatively disposed in respective ones of said pneumatic cylinders, each of said pneumatic pistons including respective shafts protruding inwardly beyond said pneumatic cylinders, a metering tube fixedly disposed in spaced relationship with and coaxially disposed with respect to said body and said pneumatic pistons, a cushioning valve spool slideably disposed in said metering tube, said cushioning valve spool when in central position being proximate with the ends of both of said shafts, said cushioning valve spool including a central valve head and a pair of lobe heads disposed on respective sides of said valve head, said valve spool and said pneumatic cylinders forming chambers delineated thereby and by said valve head and head lobes, said metering tube including aperture means disposed in each of said chambers when said cushioning valve spool is in its central position, said valve head of said cushioning valve spool being dimensioned with respect to pneumatic piston travel for translational movement across said apertures means of said metering tube which is present between said valve head and said lobe heads when said valve spool is in a central position, partition means disposed between said cylindrical body and said metering tube at a region in line with the nominal position of said valve head of said cushion valve spool, said source being connected to said pneumatic cylinders, and said cylindrical body being provided apertures communicating with said respective ones of said line portions, said cushioning valve spool, pneumatic cylinders and pneumatic pistons being so constructed and arranged that translations of said cushioning valve spool produce corresponding translations of said piston shafts and said pneumatic pistons to which they are connected for urging at a particular time a particular one of said pneumatic pistons in a compression stroke.

2. Structure according to claim 1 wherein said pneumatic cylinders are maintained at different nominal pressures.

References Cited by the Examiner UNITED STATES PATENTS 206,018 7/78 Henrich 60-545 618,464 1/99 Kelley 91-461 766,667 8/04 Cheshire 60-52 992,161 5/11 Catlin 91-461 1,711,967 5/29 Robson 60-52 1,764,098 6/30 Galloway 91-27 2,069,214 2/37 Carlson 91-437 X 2,251,729 8/41 Bach 91-437 2,380,596 7/45 Hertrich 60-54 2,454,551 11/48 Carlson 91-438 2,655,384 10/53 Peterson 91-454 2,680,491 6/54 Davidson 91-437 2,742,922 4/56 Frellsen 137-62569 2,965,133 12/60 Rice 91-437 X 2,968,282 1/61 Hayman 91-437 SAMUEL LEVINE, Primary Examiner. 

1. IN A FEEDWORKS HAVING A GUNE LINE, A RETURN LINE DISPOSED IN COMMUNICATION WITH SAID GUN LINE AT A JUNCTURE THEREWITH, A PISTON TRANSLATIONALLY DISPOSED IN SAID GUN LINE, A RECIPROCABLE PISTON ROD AFFIXED TO SAID PISTON AND DISPOSED WITHIN, JORUNALED BY, AND EXTENDING BEYOND SAID GUN LINE, AND ADAPTED TO RECIPROCATE AN EXTERNAL GIVEN MASS, AND MEANS AFFIXED TO AND DISPOSED IN COMMUNICATION WITH CORRESPONDING LINE PORTIONS OF SAID GUN CYLINDER AND SAID RETURN CYLINDER REMOTE FROM SAID JUNCTURE FOR FORCING LIQUID IN SAID LINES AGAINST SAID PISTON IN OPPOSITE DIRECTIONS, ALTERNATELY, FOR TRANSLATING SAID PISTON; AN IMPROVEMENT COMPRISING A SOURCE OF COMPRESSED GASEOUS MEDIA, AND PNEUMATICALLY CONTROLLED CUSHIONING MEANS COUPLED TO SAID SOURCE AND CONNECTED IN AUTOMATICALLYSHUTING CIRCUIT RELATIONSHIP WITH SAID GUN CYLINDER AND SAID RETURN CYLINDER AT SAID LINE PORTIONS FOR AUTOMATICALLY SHUNTING IN A METERED MANNER FLUID APPROACHING ONE OF SAID LINE PORTIONS OF SAID GUN AND RETURN LINES INTO THE EXTREMITY OF THE REMAINING LINE, TO THEREBY CUSHION TRANSIENT FLUID RESPONSE, AND WHEREIN SAID PNEUMATICALLY CONTROLLED CUSHIONING MEANS INCLUDES A CYLINDRICAL BODY, A PAIR OF PNEUMATIC CYLINDERS FIXEDLY DISPOSED ON OPPOSITE SIDES OF SAID BODY, A PAIR OF PNEUMATIC PISTON OPERATIVEY DISPOSED IN RESPECTIVE ONES OF SAID PNEUMATIC CYLINDERS, EACH OF SAID PHEUMATIC PISTONS INCLUDING RESPECTIVE SHAFTS PROTRUDING INWARDLY BEYOND SAID PNEUMATIC CYLINDERS, A METERING TUBE FIXEDLY DISPOSED IN SPACED RELATIONSHIP WITH AND COAXIALLY DISPOSED WITH RESPECT TO SAID BODY AND SAID PNEUMATIC PISTONS, A CUSHIONING VALVE SPOOL SLIDEABLY DISPOSED IN SAID METERING TUBE, SAID CUSHIONING VALVE SPOOL WHEN IN CENTRAL POSITION BEING PROXIMATE WITH THE ENDS OF BOTH OF SAID SHAFTS, SAID CUSHIONING VALVE SPOOL INCLUDING A CENTRAL VALVE HEAD AND A PAIR OF LOBE HEADS DISPOSED ON RESPECTIVE SIDES OF SAID VALVE HEAD, SAID VALVE SPOOL AND SAID PNEUMATIC CYLINDERS FORMING CHAMBERS DELINEATED THEREBY AND BY SAID VALVE HEAD AND HEAD LOBES, SAID METERING TUBE INCLUDING APERTURE MEANS DISPOSED IN EACH OF SAID CHAMBERS WHEN SAID CUSHIONING VALVE SPOOL IS IN ITS CENTRAL POSITION, SAID VALVE HEAD OF SAID CUSHIONING VALVE SPOOL BEING DIMENSIONED WITH RESPECT TO PNEUMATIC PISTON TRAVEL FOR TRANSLATIONAL MOVEMENT ACROSS SAID APERTURES MEANS OF SAID METERING TUBE WHICH IS PRESENT BETWEEN SAID VALVE HEAD AND SAID LOBE HEADS WHEN SAID VALVE SPOOL IS IN A CENTRAL POSITION, PARTITION MEANS DISPOSED BETWEEN SAID CYLINDRICAL BODY AND SAID METERING TUBE AT A REGION IN LINE WITH THE NORMAL POSITION OF SAID VALVE HEAD OF SAID CUSHION VALVE SPOOL, SAID SOURCE BEING CONNECTED TO SAID PNEUMATIC CYLINDERS, AND SAID CYLINDRICAL BODY BEING PROVIDED APERTURES COMMUNICATING WITH SAID RESPECTIVE ONES OF SAID LINE PORTIONS, SAID CUSHIONING VALVE SPOOL, PNEUMATIC CYLINDERS AND PNEUMATIC PISTONS BEING SO CONSTRUCTED AND ARRANGED THAT TRANSLATIONS OF SAID CUSHIONING VALVE SPOOL PRODUCE CORRESPONDING TRANSLATIONS OF SAID PISTON SHAFTS AND SAID PNEUMATIC PISTONS TO WHICH THEY ARE CONNECTED FOR URGING AT A PARTICULAR TIME A PARTICULAR ONE OF SAID PNEUMATIC PISTONS IN A COMPRESSION STROKE. 